U.S. officials have expressed concern that an international court ruling expected in coming weeks on a case brought by the Philippines against China over its South China Sea claims could prompt Beijing to declare it an air defense identification zone, or ADIZ, as it did to the north, in the East China Sea, in 2013.

Work told an event hosted by the Washington Post that the United States would not recognize such an exclusion zone in the South China Sea, just as it did not recognize the one in the East China Sea.